Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the first occurrence within the range of elements in the List<T> that starts at the specified index and contains the specified number of elements.

Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the first occurrence within the range of elements in the List<T> that extends from the specified index to the last element.

Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List<T> that contains the specified number of elements and ends at the specified index.

Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List<T> that extends from the first element to the specified index.

Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the List<T> that starts at the specified index and contains the specified number of elements.

Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the List<T> that contains the specified number of elements and ends at the specified index.

Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.(Defined by Enumerable.)

Overloaded. Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.(Defined by Enumerable.)

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.(Defined by Enumerable.)

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.(Defined by Enumerable.)

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.(Defined by Enumerable.)

Overloaded. Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.(Defined by Enumerable.)

Overloaded. Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.(Defined by Enumerable.)

Overloaded. Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element.(Defined by Enumerable.)

Overloaded. Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.(Defined by Enumerable.)

Overloaded. Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.(Defined by Enumerable.)

Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.(Defined by Enumerable.)

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

The List<T> class is the generic equivalent of the ArrayList class. It implements the IList<T> generic interface by using an array whose size is dynamically increased as required.

Methods such as BinarySearch and Sort use an ordering comparer for the list elements. The default comparer for type T is determined as follows. If type T implements the IComparable<T> generic interface, then the default comparer is the CompareTo(T) method of that interface; otherwise, if type T implements the nongeneric IComparable interface, then the default comparer is the CompareTo(Object) method of that interface. If type T implements neither interface, then there is no default comparer, and a comparer or comparison delegate must be provided explicitly.

The List<T> is not guaranteed to be sorted. You must sort the List<T> before performing operations (such as BinarySearch) that require the List<T> to be sorted.

Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

For very large List<T> objects, you can increase the maximum capacity to 2 billion elements on a 64-bit system by setting the enabled attribute of the configuration element to true in the run-time environment.

In deciding whether to use the List<T> or ArrayList class, both of which have similar functionality, remember that the List<T> class performs better in most cases and is type safe. If a reference type is used for type T of the List<T> class, the behavior of the two classes is identical. However, if a value type is used for type T, you need to consider implementation and boxing issues.

If a value type is used for type T, the compiler generates an implementation of the List<T> class specifically for that value type. That means a list element of a List<T> object does not have to be boxed before the element can be used, and after about 500 list elements are created the memory saved not boxing list elements is greater than the memory used to generate the class implementation.

It is to your advantage to use the type-specific implementation of the List<T> class instead of using the ArrayList class or writing a strongly typed wrapper collection yourself. The reason is your implementation must do what the .NET Framework does for you already, and the common language runtime can share Microsoft intermediate language code and metadata, which your implementation cannot.

The List<T> class is used infrequently in F# code. Instead, Lists (F#), which are immutable, singly-linked lists, are typically preferred. An F# List provides an ordered, immutable series of values, and is supported for use in functional-style development. When used from F#, theList<T> class is typically referred to by the ResizeArray<'T> type abbreviation to avoid naming conflicts with F# Lists

The following example demonstrates several properties and methods of the List<T> generic class of type string. (For an example of a List<T> of complex types, see the Contains method.)

The default constructor is used to create a list of strings with the default capacity. The Capacity property is displayed and then the Add method is used to add several items. The items are listed, and the Capacity property is displayed again, along with the Count property, to show that the capacity has been increased as needed.

The Contains method is used to test for the presence of an item in the list, the Insert method is used to insert a new item in the middle of the list, and the contents of the list are displayed again.

The default Item property (the indexer in C#) is used to retrieve an item, the Remove method is used to remove the first instance of the duplicate item added earlier, and the contents are displayed again. The Remove method always removes the first instance it encounters.

The TrimExcess method is used to reduce the capacity to match the count, and the Capacity and Count properties are displayed. If the unused capacity had been less than 10 percent of total capacity, the list would not have been resized.

Finally, the Clear method is used to remove all items from the list, and the Capacity and Count properties are displayed.

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

It is safe to perform multiple read operations on a List<T>, but issues can occur if the collection is modified while it’s being read. To ensure thread safety, lock the collection during a read or write operation. To enable a collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. For collections with built-in synchronization, see the classes in the System.Collections.Concurrent namespace. For an inherently thread–safe alternative, see the ImmutableList<T> class.